The present invention relates to a material of a soft magnetic thin film for use in a magnetic head for recording/reproducing information on/from a magnetic disc device, a method of manufacturing the soft magnetic thin film, a magnetic head using the soft magnetic thin film and a magnetic storage unit using the magnetic head.
Conventionally, a Ni--Fe (permalloy) alloy plated film is generally used as a write head material but this Ni--Fe alloy plated film is disadvantageous in that it has a small saturation magnetic flux density Bs of 0.8 to 1.0 tesla (T). In addition, since the Ni--Fe alloy plated film has a small resistivity of 20 .mu..OMEGA.cm, the phase of a recording magnetic field is delayed owing to an eddy current during high-frequency recording and disadvantageously recording characteristics are deteriorated.
Accordingly, for the purpose of realizing ultrahigh density recording, a magnetic pole material for magnetic head having a larger saturation magnetic flux density than that of at least the Ni--Fe alloy and a high resistivity has been desired to be developed.
To solve the above problems, the following literatures have already reported a Co--Fe (Permendur) system film or a Co--Ni--Fe (Perminvar) system film.
Firstly, IEEE Transactions on Magnetics, by S. H. Liano, Vol. Mag-23, No. 5, pp-2981-2983 (hereinafter called prior art 1) discloses that better characteristics or properties can be obtained when Co--Fe is used for a magnetic pole piece of a magnetic head than when Ni--Fe is used.
Also, Magnetic Recording Research Meeting of the Institute of Electronics Information and Communication Engineers of Japan, by Omata, MR 88-23 (1988) (hereinafter referred to as prior art 2) describes that a Co--Ni--Fe thin film for use in a magnetic head is formed through evaporation and alloy electrodeposition process.
Also, Journal of The Japan Society of Applied Magnetics, by Shinoura et al, Vol. 18, No. 2, page 277 (1994) (hereinafter called prior art 3) shows a Co--Ni--Fe alloy electrodeposited film for magnetic head.
Further, JP-A-60-82638 (hereinafter called prior art 4) discloses a ternary alloy thin film consisting of, by weight %, Ni.ltoreq.75%, 10 to 90% Co and Fe.ltoreq.15%, having magnetostriction in the range of .+-.2.times.10.sup.-6 and coercive force Hc.ltoreq.10 Oe and being used in a magnetic core of a thin film magnetic head.
Further, JP-A-62-71015 (hereinafter called prior art 5) discloses that in a thin film magnetic head having upper and lower magnetic films, each of the upper and lower magnetic films is formed of an alloy thin film consisting of, by weight, 3 to 30% Ni, 62 to 95% Co and 2 to 8% Fe and having a face-centered cubic (FCC) structure.
Further, JP-A-2-68906 (hereinafter referred to as prior art 6) discloses a soft magnetic film made of an alloy consisting of, by atomic %, 20 to 70% Ni, 5 to 45% Co and 20 to 75% Fe and added with less than 5% Cr, Ti, Zr and Hf.
The above prior arts show that with the Co--Fe film or the Co--Ni--Fe plated film, a saturation magnetic flux density Bs of, for example, 1.8 T can be obtained which is higher than that of the conventional Ni--Fe (permalloy) film.
However, the above prior arts in no way refer to the resistivity and fail to disclose any solution to the aforementioned increasing resistivity.
More particularly, the above prior arts disclose the magnetic pole material which has a high saturation magnetization (Bs) in order that sufficient information can be written to a recording medium having a high coercive force for the purpose of realizing high-density recording. However, the prior arts do not disclose any magnetic pole material which has a high resistivity in addition to the high saturation magnetization to cope with such a problem encountered in high-frequency recording during high-density recording that eddy current is caused owing to the small resistivity of the conventional material (for example, 20 .mu..OMEGA.cm of the permalloy film), with the result that the phase of a recording magnetic field is delayed and recording characteristics or properties of the magnetic head are deteriorated.